Right now I have a 9800GX2 on a Maximus Formula board. Since I need dual monitor display out of it, I would have to disengage SLI before I can do anything. Without SLi the FPS drops quite dramatically, and I would like to have it on. Now I'm thinking I should use the other PCI-e slot on my mobo to accommodate another nvidia card for the second display, say an 8600GT

Can it be done with 9800GX2 still in internal SLi and with 8600GT powering another monitor?

Windows can become VERY VERY unhappy mixing two different types of driver installs.

I've used an X600 and an 8800GTX just fine under both XP and Vista. On XP you can install both drivers, but I didn't ever find it was necessary and the stock VGA driver worked fine for 1024*768. With Vista you can't install the ATI driver, but the stock Vista driver is much more capable than the XP one so it should be no problem as long as you don't need too high of a resolution on the 2nd monitor.

Right now I have a 9800GX2 on a Maximus Formula board. Since I need dual monitor display out of it, I would have to disengage SLI before I can do anything. Without SLi the FPS drops quite dramatically, and I would like to have it on. Now I'm thinking I should use the other PCI-e slot on my mobo to accommodate another nvidia card for the second display, say an 8600GT

Can it be done with 9800GX2 still in internal SLi and with 8600GT powering another monitor?